The invention relates to ventilation systems for buildings and, more particularly, to ventilation systems that are used in swine finishing shelters.
The swine industry is rapidly adopting the total confinement approach to managing and raising hogs. The approach consists of keeping swine continuously confined within a building from the time of birth to the time they are delivered to market. It has been found that total confinement can result in increased hog production as well as much improved working conditions for the farmer. On the other hand, confinement can also produce undesirable conditions for the animals which heretofore have not existed. These conditions vary considerably depending on the season of the year. In particular, care must be taken in the winter to preserve heat within the building, while in the summer heat and moisture are undesirable conditions. Additionally, toxic fecal gases are always a problem. To alleviate undesirable, confinement conditions, a properly designed ventilation system is a necessity.
Pig raisers basically use two types of swine shelters. During the milder times of the year--late spring, summer, and early autumn--an open shelter which has a roof and less than four sidewalls may be used. During harsher periods such as late fall, winter, and early spring hogs may be confined within a totally closed shelter. Or, as indicated previously, the closed shelter concept may be utilized year-around.
In an open shelter, the swine are allowed to range outside or to enter the building to gain protection from the sun or inclement weather. A special ventilation system is unnecessary since air is readily and continuously exchanged through the one or more open sides of the building. The open shelter concept is economical and works under proper climatic conditions.
In a closed shelter, a ventilation system is a necessity, and the prior art shows a variety of systems. One such system appears in U.S. Pat. No. 3,951,336. It uses pressure and temperature sensors to operate a series of baffles and fans. Somewhat less complex is the system shown in U.S. Pat. No. 3,601,096. It uses air inlets formed at the juncture of the sidewalls and the roof and a plurality of air outlets located in the center of the roof with thermostatically-controlled fans therein. Other prior art systems use various types of eave or sidewall inlet openings in conjunction with various exhaust-duct arrangements. See, for example, U.S. Pat. Nos. 2,708,868 and 1,615,964. In summary, the prior art shows an expensive, completely-automated, environmental control system which conceivably could be used year-around, and it shows less-expensive ventilation systems which would be adequate on a seasonal basis, but not year-around.